The present invention relates to track accessing arm movement in disc drive systems. More specifically, the present invention relates to a magnet/block assembly that creates and distributes a permanent magnetic field which interacts with a transient magnetic field produced by an actuator coil that is connected to a track accessing arm in a disc drive system.
In a disc drive system, transducer head assemblies write and retrieve data from concentric tracks of magnetic media discs. A transducer head assembly is typically connected to a resilient member, such as a gimbal spring, which in turn is connected to an end of a track accessing arm.
An actuator coil is connected to an end of the track accessing arm opposite the end that carries the transducer head assembly. The actuator coil is placed within a gap space of a magnet/block assembly. The magnet/block assembly includes permanent magnets, which create a permanent magnetic field, and a block, typically formed of materials having ferromagnetic properties. Between the two ends of the track accessing arm is an actuator spindle that forms an axis of rotation intermediate the actuator coil and the transducer head assembly.
Applying a current to the actuator coil positions and holds the transducer head assembly over various concentric tracks of the magnetic media disc. The current applied to the actuator coil produces a transient magnetic field that interacts with the permanent magnetic field in the gap space of the magnet/block assembly. The interaction between the two magnetic fields rotates the track accessing arm along the axis of rotation. The rotation of the track accessing arm moves the transducer head assembly between various concentric tracks of the magnetic media disc.
In one embodiment of the prior art, a magnet/block assembly comprises permanent magnets and a two piece block that includes a back iron separated from a front iron by a gap space. The permanent magnets produce a magnetic field that is distributed in the gap space. A magnet/block assembly of this type may have two or four magnets placed in the gap space. One example of this type of magnet/block assembly is disclosed in Levy et al. U.S. Pat. No. 4,796,122.
In another embodiment found in the prior art, a magnet/block assembly has three prongs that form two gap spaces between the prongs. An actuator coil having a hollow center surrounds the center prong with part of the coil in the first gap space and another part of the coil in the second gap space. The magnet/block assembly is formed with an open end and a closed end. A plate, or loop, is attached to the open end after the actuator coil is placed around the center prong. The plate, or loop, connects the three prongs and forms a flux conduction path. While this type of block can be formed integrally, the block has two gap spaces, and therefore requires more permanent magnets than does a block that has a single gap space. Examples of this type of magnet/block assembly are disclosed in Brand et al. U.S. Pat. No. 4,710,834, Wright U.S. Pat. No. 4,805,055, Chalmers et al. U.S. Pat. No. 4,890,174 and Yoshioka U.S. Pat. No. 4,941,062.